The human body has numerous conduits such as blood vessels carrying fluid to essential tissues and areas for circulation or excretion. When conduits become damaged, severed or wholly occluded due to physiological problems or diseases, certain sections must be bypassed to allow for the free and continuous flow of fluids. Anastomosis is performed for the purpose of connecting different conduits together to optimize or redirect flow around a damaged or occluded portion of a conduit.
In the context of the peripheral vascular and/or the cardiovascular system, atherosclerosis, a common vascular disease, can cause partial blockage or complete occlusion of an arterial vessel, resulting in restricted blood flow and therefore compromised perfusion to the tissue served by the blood flow. In the case of an occluded or partially occluded coronary vessel, for example, an area of the heart's myocardium would be compromised, which can lead to a myocardial infarction, or other ischemic heart syndrome such as congestive heart failure. In the case of peripheral vascular atherosclerotic disease, occluded vessels lead to ischemic syndromes such as threatened limbs, stroke and other morbidities. In many cases, such a blockage or restriction in the blood flow leading to the heart or peripheral vessels can be treated by a surgical procedure known as an artery bypass graft procedure.
A bypass procedure involves the establishment of an alternate blood supply path to bypass a diseased section of a diseased or compromised artery. In the bypass procedure, the surgeon typically dissects one end of a source or “pedicled” artery (such as the internal mammary artery in the case of coronary artery bypass), or harvests a free vessel segment (typically the saphenous vein in the leg), to use as a graft conduit to bypass the obstruction in the affected artery to restore normal blood flow. The graft vessel is connected to the obstructed vessel by means of an anastomosis procedure wherein an opening in the graft vessel is sutured to the obstructed vessel at an arteriotomy site made within the obstructed vessel. A side-to-side anastomosis procedure involves the attachment of two vessels at incised locations (e.g., arteriotomies) within a side wall of each of the vessels. An end-to-side anastomosis procedure involves the attachment of two vessels at an incised location within a side wall of one of the vessels and at the transected end of the other vessel.
Other applications in which anastomosis is employed include the creation of an arterial to venous fistula for the purpose of either creating a dialysis access site, or, as an alternative means of creating arterial revascularization by “arterializing” a vein through creation of a conduit past the occlusive disease. The latter is often employed in treating peripheral vascular disease but is used in coronary applications as well.
The patency of the anastomosis is crucial to a successful bypass, both by acute and long-term evaluation. Patency may be compromised by technical, biomechanical or pathophysiological means. Among the technical and biomechanical causes for compromised patency (also termed restenosis) are poorly achieved anastomoses, whether induced by poor placement, trauma at the anastomosis site or biological responses to the anastomosis itself. Improperly anastomosed vessels may lead to leakage, create thrombus and/or lead to further stenosis at the communication site, possibly requiring re-operation and further increasing the risk of stroke. As such, forming the anastomosis is the most critical procedure in bypass surgery, requiring precision and accuracy on the part of the surgeon.
The current gold standard for forming the anastomosis is by means of suturing openings (natural or artificial) in the vessels together. Surgeons must delicately sew the vessels together being careful not to suture too tightly so as to tear the delicate tissue, thereby injuring the vessel which may then result in poor patency of the anastomosis. On the other hand, surgeons sometimes inadvertently suture too loosely or do not properly place the sutures so as to provide continuous seal around the arteriotomy site, resulting in leakage of fluid from the anastomosis. In addition to creating a surgical field in which it is difficult to see, leakage of fluid from the anastomosis can cause serious drops in blood pressure, acute or chronic. The loss of blood may cause other deleterious effects on the patient's hemodynamics that may even endanger the patient's life. In addition to the inherent inconsistencies in suture tightness, placement and stitch size and the lack of reproducibility, suturing an anastomosis can be very time consuming.
Advances in anastomotic instruments have been devised in the attempt to provide greater reproducibility of a precise anastomosis and to reduce the time that is required to complete an anastomosis and the necessary size of the surgical field. Many of these new instruments are stapling devices which deploy one or more staples at the anastomotic site in a single-motion action. While stapling techniques have been found to be successful in gastrointestinal procedures, due to the large size and durability of the vessels, it is less adequate for use in vascular anastomosis where the vessels are much smaller.
The manufacturing of stapling instruments small enough to be useful for anastomosing smaller vessels, such as coronary arteries, is very difficult and expensive. As stapling instruments are typically made of at least some rigid and fixed components, a stapler of one size will not necessarily work with multiple sizes of vessels. This requires a surgeon to have on hand at least several stapling instruments of varying sizes. This may significantly raise the cost of the equipment and ultimately the cost of the procedure.
Stapling instruments and staples which are adapted to conform to the smaller sized vessels are difficult to maneuver and, thus, a great deal of time, precision, and fine movement is necessary to successfully approximate the vessel tissue. Often stapling or similar coupling devices require the eversion of the vessel walls to provide intima-to-intima contact between the anastomosed vessels. Everting may not always be practical especially for smaller arteries because of the likelihood of tearing when everted. Another factor which may lead to damage or laceration of the vessel and/or leakage at the anastomosis site is the variability of the force that a surgeon may use to fire a stapling instrument causing the possible over- or under-stapling of a vessel. Still other factors include the unintended inversion of the vessel edges and the spacing between staple points. Rectifying a poorly stapled anastomosis is itself a complicated, time-consuming process which can further damage a vessel.
The tension and/or compression forces exerted on the vessel walls as a result of suturing and stapling can result in damage to the vessel wall, even to the extent of causing tissue necrosis. Damage to the intima of a vessel is particularly problematic as it may inhibit the natural bonding process that occurs between the anastomosed vessels and which is necessary for sufficient patency. Furthermore, damaged vessel walls are likely to have protuberances that, when exposed to the blood stream, could obstruct blood flow or may produce turbulence which can lead to formation of thrombus, stenosis and possible occlusion of the artery.
As cardiac surgery is moving into less invasive procedures, surgical access is being reduced, forcing surgeons to work in constantly smaller surgical fields. These procedures are made more difficult due to the multiple characteristics that are unique to each anastomosis and to each patient. For example, the arteries' internal diameter dimensions are difficult to predict and the inside walls are often covered with deposits of stenotic plaque which creates the risk of dislodging plaque into the patient's blood stream during the anastomosis procedure. The resulting emboli in turn create a greater risk of stroke for the patient. The dislodgement of plaque is most likely to occur when the vessel wall undergoes trauma such as the puncturing, compression and tension exerted on the vessel by suturing and stapling. The vessel walls can also be friable and easy to tear, and are often covered with layers of fat and/or are deeply seated in the myocardium, adding to the difficulty of effectively and safely performing conventional anastomotic procedures.
Many of the drawbacks of the above mentioned anastomotic connectors and techniques have been obviated by recent technological advancements. In particular, novel anastomotic connectors have been developed which avoid compression, tensioning and puncturing of the vessel tissue. Examples of such anastomotic connectors are disclosed in U.S. Pat. Nos. 6,165,185 and 6,251,116, copending U.S. patent application Ser. No. 10/235,948, entitled “Devices and Methods for Interconnecting Conduits and Closing Openings in Tissue”, attorney docket no. VASC009 to Akin, et al., filed on even date herewith; and in U.S. Patent Application Publication No. US-2001-0044631-A1, which are herein incorporated by reference. These devices include at least one flexible member in the form of a sheet, membrane or flange which is adapted to conform to and seal with an inner surface or circumference of a vessel into which it is delivered. The flexible member is adapted to utilize only the internal vessel pressure, e.g., blood pressure, exerted thereon to form a substantially fluid-tight seal with the inner surface of the conduit whereby substances within the vessel are prevented from leaking from the artificial opening under normal physiological conditions. As such, these devices obviate the need to compress, puncture or place tension on the vessel tissue and reduce many of the risks associated with prior anastomotic and closure devices. Another advantage of these flexible devices is that they can be made from materials which are biodegradable or bioresorbable, such as degradable hydrogels, polymers, protein cell matrices, plant or carbohydrate derivatives (sugars), and the like.
Unlike staples, clips, sutures and the like which often require the surgeon to employ many components for their delivery and implantation in the body, the flexible flanges or membranes may be implanted manually by a surgeon. As such, the use of cumbersome and complicated instrumentation necessary for implanting the devices is avoided. However, the ongoing desire to reduce the size of the surgical opening necessitates the use of minimally invasive delivery devices and techniques, and minimizes the attractiveness of manual implantation of the anastomotic connectors.
Thus, it is desirable to provide minimally invasive devices and techniques for the delivery and implantation of these advanced anastomotic connectors which reduce the access space necessary for performing an anastomosis compared to conventional techniques. It would be additionally beneficial and desirable if such instrumentation was easy to use, minimized the procedure time, minimized the risk of improper alignment between the conduits, and minimized the risk of leakage, tearing and damage at the anastomosis site. It is additionally desirable to provide such delivery devices in which a single configuration may be employed with a variety of configurations of anastomotic connectors, including both side-to-side and end-to-end devices. Further, it would be highly advantageous if such delivery devices were usable for both proximal and distal anastomosis applications, e.g., a graft vessel to the aorta and a graft vessel to a native vessel at a location downstream of the stenotic lesion within the native vessel, respectively.
These and other objects, advantages, and features of the invention will become apparent to those persons skilled in the art upon reading the details of the methods and systems of the present invention which are more fully described below.